So-called uncontained engine failures are thankfully very rare in aviation but that is what happened to a United Airlines Boeing 777-200 on 20th February, shortly after takeoff from Denver.
The twin-jet landed back at the airport safely and there were no injuries. A lot of debris fell in the area but again it appears that there were no injuries, only some property damage.
The PW4077 engine was built by Pratt & Whitney and the aircraft entered service in 1995.
The FAA ordered inspections on similar P&W engines while Boeing recommended operators ground their jets temporarily while inspections were carried out. United is the only operator of P&W-powered “Triple 7s” in the US; Japan Air Lines and Korean Air are other operators of this aircraft configuration.
Aircraft are rigorously tested to ensure they can handle incidents such as bird strikes/ingestion and blade-root failures, to ensure the high-energy debris cannot pierce the engine cowling.
the latest details are available from the Flight Safety Foundation.
US magazine Aviation International News has posted a video discussion on the incident.